Press for compressing pulverulent products

ABSTRACT

A PRESS FOR FORMING PULVERULENT MATERIAL TO WHICH A FLOATING DIE-CARRYING PLATE IS RESILIENTLY SUPPORTED TO YIELD DURING COMPRESSION, A PUNCH-SUPPORT PLATE IS LOCATED BELOW THE DIE-CARRYING PLATE ON A FIXED BED, A LIFTING DEVICE IS PROVIDED FOR THE PUNCH-SUPPORT PLATE, A CORESUPPORT PLATE BELOW THE PUNCH-SUPPORT PLATE, A COREPARALLEL WITH THE COMPRESSION AXIS, A PLATE BELOW THE CORE-SUPPORT PLATE, SUPPORTED BY A LIFTING DEVICE AND COUPLED TO A FLOATING PUNCH-SUPPORT PLATE BY RODS PASSING THROUGH THE CORE-SUPPORT PLATE AND PUNCH-SUPPORT PLATE, A STOP LIMITING THE MINIMUM DISTANCE OF THE PUNCH-SUPPORT PLATE AND THE CORE-SUPPORT PLATE.

Oct. 12,1911 L. A. HEDIN 3,611,498

PRESS" COMPRESSING PULVERULENT PRODUCTS Filed June 20. 1969 6 Sheets-Sheet 1 FIG 7 Oct. 12, 1971 ED 3,611,498

PRESS FOR COMPRESSING PULVERULENT PRODUCTS Filed June 20, 1969 I I Sheets-Sheet 2 21 E 22 6 I 5/ 7 LI /23 6/ -I s g m 0 o 1 Z I I 6 I I I I I I; 9 I I Oct. 12, 1971 L. A. HEDIN PRESS FOR COMPRESSING PULVERULENT PRODUCTS Filed June 20, 1969 6 Sheets-Sheet 4- Oct. 12, 1971 Em 1,498

PRESS FOR COMPRESSING PULVERULENT PRODUCTS Filed June 20, 1969 6 Sheets-Sheet 5 V///////// ///V// \H x \2 m 1% HHM U Z W@ m/ Vl/llllllllIf/IL I Oct. 12, 1971 Em PRESS FOR COMPRESSING PULVERULENT PRODUCTS Filed June 20, 1969 6 Shee'ts-Sheet 6 United States Patent 3,611,498 PRESS FOR COMPRESSING PULVERULENT PRODUCTS Louis Andr Hdin, Grenoble, France, assignor to La Metallurgie Francaise des Poudres-Metat'ram, Paris,

France Filed June 20, 1969, Ser. No. 835,114 Claims priority, appliizgio p 9France, Aug. 2, 1968,

Int. 01. B501) 11/00 US. Cl. 18--16.7 4 Claims ABSTRACT OF THE DISCLOSURE The invention relates to an improvement to a press for compressing pulverulent products which is very advantageous for manufacturing by sintering mechanical members having zones of different thicknesses.

The manufacture of metal members by sintering comprises a first operation during which the powder is compressed in the die by means of a set of top and bottom punches, possibly using cores for members formed with a bore.

There are various kinds of presses for compressing powders which operate with different cycles of movement of the die and the two punches. More particularly a so-called floating die press is known in which the bottom punch is fixed, the top punch is mobile, and the die can make a limited and controlled movement solely under the action of the frictional forces during compressing.

When the mechanical member comprises zones of different thicknesses, measured in the direction of compression, punches must be used in a number of independent portions each corresponding to a zone of different thickness of the mechanical member, since to obtain a homogeneous mechanical member, in each of these zones the powder must be subjected to an identical compression rate, so that the compressing stroke is greater in the thickest zones.

As a rule, for the thickest zones of the mechanical member use is made of a fixed bottom punch member in relation to which the whole stroke of the top punch is a compressing stroke. For the thinner portions of the member to be manufactured, the bottom punch is floatingi.e., it is mounted on a resilient device allowing it to make a certain movement during compressing which reduces by the same amount the actual compression travel of the top punch.

In the floating die kind of press, the member is ejected after compression by raising the bottom punches which therefore drive the member out of the die.

In the prior art presses, the same bottom plate acts as a bearing for the fixed bottom punch, the floating bottom punches, their adjusting device and their spring device producing a counterpressure, and also for the cores. This sameplate therefore receives the thrust required for injecting the member after it has been compressed.

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Consequently, adjustments in position of the or each core, the punches, and more particularly the floating punches, are concentrated in the same zone which is moreover made inaccessible by the thrust device associated with the plate for ejection purposes.

Adjustment of any one of these members therefore means that the supporting plate must be completely dismantled every time, and this substantially lengthens the time taken to set up the press for the manufacture of a fresh product.

Moreover, it is difficult to influence the counterpressure exerted on the die-carrying plate and the counterpressure exerted on the floating punches during the stroke which brings them finally into abutment with the bearing plate. The result is local differences in the compression rate of the powder in the member produced.

The invention obviates this disadvantage, making all the adjustment systems for all the tools permanently accessible; according to the invention the press comprises a floating die-carrying plate resiliently connected to the frame and adapted to move in the direction of compression between adjustable stops; a supporting plate for the bottom punches which bears against a fixed bed-plate connected to the frame, the punch-supporting plate being connected to a lifting device via rigid peripheral rods leaving the central portion of the plate free; a core-supporting plate which is independent and disposed below the punchsupporting plate, which is connected to the frame with facilities for adjustment in the direction of compression, the cores extending into orifices extending through the puinch-supporting plate; a plate supporting the rods for adjusting the floating bottom punches which is independent and is disposed below the core-supporting plate, mounted on a resiliently acting lifting device, the adjusting rods for the floating punches extending into orifices extending through the core-supporting plate, and into corresponding orifices extending through the punch-supporting plate, each adjusting rod being adjustably connected to a strut extending through the core-supporting plate and limiting to a fixed value the minimum distance between the supporting plate for the adjusting rods and the supporting plate for the bottom punches.

The invention will now be described in greater detail with reference to an exemplary embodiment thereof illustrated in the drawings.

FIG. 1 is a sectional view of a typical member which can be produced on the machine to be described hereinafter, which is equipped with the tools required for a member of this shape;

FIGS. 2-4 are diagrammatic sections through a floating matrix press according to the invention, showing various phases of the operational cycle of the machine, FIG. 2 corresponding to the end of the phase of filling the die with metal powder, FIG. 3 corresponding to the end of the compressing phasei.e., the maximum compression point, FIG. 4 corresponding to the end of the ejection phase of the compressed member;

FIG. 5 corresponds to an adjusting position of the machine;

FIG. 6 is a detail of the device for simultaneously adjusting the stops of the die-carrying plate; and

FIG. 7 is a graph showing the operational cycle of the machine and indicating the relative movement of its various moving members.

The member shown in section in FIG. 1 is formed with a bore and has two zones h h of different thicknesses, so that the machine will have a two-part bottom punch and a core which extends through the die and engages in the top punch and in one of the bottom punches.

Referring to FIG. 2, a frame 1 takes the compressing force via a transverse bed-plate 2 which is a fixed member of the press framework. A die 3, in which the powder is compressed, is retained in a die-carrying plate 4 bearing against double-acting jacks 5 whose feed pressure p can be adjusted.

The plate 4 is guided in its vertical movement by four guide columns (not shown) and by two columns 6 connected to the plate 4 and engaging through bed-plate 2 and in elements of the frame 1. The travel of the plate 4 is limited at the top by nuts 8 which can be adjusted on rods 7, and at the bottom by nuts 9 which can be adjusted on the columns 6. The device for adjusting the nuts simultaneously will be described hereinafter.

Bearing against the fixed bed-plate 2 is a punch-supporting plate 10 connected to a plate 12, terminating in a sheath 13, by four rods 11 extending through fixed bed-plate 2. The sheath 12 is connected at a plate 14 to a lever 15 articulated to the frame at a place 16 and connected via a link 17 to the general press-driving mechanism (not shown).

To manufacture the member shown in FIG. 1, use is made of a top punch 20, a floating bottom punch 21, and a bottom punch 22 which is fixed during compressing. The bore in the member is produced by a core 23 extending through the punch 22. The floating punch 21 bears against plate 24 via an adjusting rod 25 and a nut and lock-nut assembly 26. A tubular strut 27 bears against the nut and lock-nut assembly 26 and abuts below the punch supporting plate 10 when the plate 24 is in the raised position. The plate 24 is mounted at the end of a sheath 28 sliding in the sheath 13. The sheath 28 is directly connected to a double-acting jack 32 rigidly connected to the frame.

Sliding inside the sheath 28 is a rod 33 connected to a double-acting jack (not shown) and adapted to displace the rod 33 in the direction shown by arrow 34.

The core-supporting plate is formed by a screw-threaded disc 40 and a plate 41, these members engaging tightly around the heel of the core 23. The disc 40 engages in a tapped bush 42 retained in position in a recess in the bed-plate 2 by a ring 43. The bush 42 is formed with a series of maneuvering apertures 44.

Referring to FIG. 6, nuts 8, engaging on screw threaded rods 7 and forming top stops for limiting the travel of the die-carrying plate 4, bear external teeth 50. The nuts 8 can be adjusted simultaneously in parallel with one another by a screw 51 borne on each side of the press by casings 52 connected to the frame. In each casing, the screw meshes with a wheel 53 connected via a shaft 54 to a pinion 55 borne by an open casing 56 connected to the frame. Each casing 56 receives a long pinion 57 which meshes with both the pinion 55' and the teeth 50 of the stop-nut 8. The length of the pinion 57 enables the nut 8 to mesh over the whole adjusting travel provided.

The nuts 9, which form bottom stops to limit the travel of the plate 4, have a substantially equivalent device for simultaneous and parallel adjustment.

As shown in FIG. 2, the press is in the filling position and the uncompressed powder occupies the Whole space 45 bounded by the die 3, punches 21, 22 and core 23, and is flush with the upper portion of the die.

The die carrying plate 4 is kept in its raised position abutting the nuts 8 by the pressure p set up in the double-acting jacks 5. The floating punch 21 is kept in the raised position by a pressure p set up in the jack 32 which keeps the plate 24 raised until the strut 27 abuts the plate 10.

During the compressing phase, the top punch 20 descends and progressively penetrates into the die. As the pressure on the powder increases, the force on the punch 21 increases and finally exceeds the force produced by the pressure 2 in the jack 32; the punch 21 then descends until its heel abuts the plate 10.

Similarly, the compression of the powder sets up on the die walls a frictional component which, when it exceeds the force produced by the pressure p in the jacks 5, entrains the downward movement of the die-carrying plate 4 until the nuts 9 abut the frame. At the end of compression the position of the press members is as shown in FIG. 3, when the member has taken on its final shape 46.

After the maximum compression point corresponding to the bottom dead-centre position of the punch 20, the latter begins to rise again. At the same time, the member 46 formed in the die is ejected by a rising movement of the punch supporting plate 10 controlled by lever 17 and 15.

During the first phase of rising of the plate 10 and the punches 21, 22, the die 3 and the die-carrying plate 4 themselves rise until they abut beneath the nuts 8. In the second phase, the die remains fixed, while the punches move the member 46 into the position shown in FIG. 4.

When a member is being compressed which is formed with a bore and is relatively high in relation to its other transverse dimensions, on ejection the sum of the fric tional forces on the inner die walls and the outside of the core may be considerable and exceed the capacity of the ejection system.

The frictional forces can be reduced by leaving the core engaged in the member during the ejection travel, thus obviating friction on the core during this operation. The slight expansion of the member after it leaves the die is reflected back in connection with the core, friction becomes substantially negligible at that place, and the core can be withdrawn very readily.

To this end use is. not made of the screw-threaded disc 40, but the core-supporting plate 41 is attached to the end of the rod 33, the plate 24 being replaced by a special plate whose centre is formed with an aperture through which the rod 33 extends. During compression, a force p is exerted by a jack in the direction indicated by arrow 34 to resist the compressing force and keep the rod 33 and the core 23 immobile, and during ejection, the rod 33 entrains the core 23 in a movement identical with that of the punches and the memberi.e., without the core moving in relation to the member. After ejection has been performed and the frictional forces on the core have been almost completely obviated, the withdrawal of the rod 33 brings the core up back into place for the following cycle.

The movement of the various tools of the machine during an operational cycle will be more clearly understood with reference to the graph (FIG. 7) which shows the movements as a function of time, operations being performed with a fixed core.

The curve 61 shows the movement of the upper plane of the die 3.

The curve 60' shows the movement of the lower plane of the top punch 20.

The curve. 62 shows the movement of the upper plane of the floating bottom punch 21.

The curve 63 shows the movement of the upper plane of the fixed bottom punch 22.

The start of the cycle is taken to be the moment T at which the top punch is in its top dead-centre position and in which the space 45 is substantially filled with powder (FIG. 2).

The top punch 20 starts to' descend at the moment T and at the moment T it penetrates into the die for the actual compressing phase which will last until T Between T and T and in spite of the counterpressure p in the jack 5, the die-carrying plate 4 slightly yields and may possibly abut the nuts 9. Similarly, the floating bottom punch 21, in spite of the counterpressure p slightly yields until it abuts; possibly the counterpressure p p can be eliminated before T FIG. 3 shows the position of the members at the moment T During T and T the rising movement of the punches ejects the member, whereas during the first portion of this period, the die-carrying plate has returned to its raised position under the action of friction and the pressure 2 sets up again in the jack 5. FIG. 4 shows the position of the members at the moment T Between T and T the bottom punches resume their starting position as a result of the force of gravity and the pressure p sets up again in the jack 32, thus enabling the die to be refilled.

During compressing, the initial thicknesses of uncompressed powder H H become respectively h 11 Which are the required dimensions of the member. H H and therefore the adjustment of the bottom punches are so determined that H 1 H 2 compression rate To adjust the various tools, the pressure in the jack 32 is reversed to lower the plate 24 completely, as it is seen in FIG. 5.

In a press of this construction, the peripheral distribution of the ejection rods 11 and the ability to lower the plate 24 completely produces a wide clearance giving access to all adjusting points (adjustment of cores and adjustment of floating punches) without the tool-carrying members having to be dismantled or moved.

Moreover, the independence of the punch-supporting plate, the core-supporting plate, and the plate-supporting the adjusting rods for the floating punches enables each tool to be adjusted separately without affecting the adjustment of the others.

The counterpressure on the floating punches is produced by a readily adjustable pneumatic pressure independently of the adjustment of the travel of the floating punches.

Of course, the scope of the invention is not exceeded by embodiments which differ from the foregoing merely exemplary description only in detail. For instance, the pneumatic jacks described could be replaced by hydraulic jacks to control the die-carrying plate or the supporting plate of the adjusting rods. Moreover, other arrangements might be used for adjusting the core-supporting plate, adjusting the stops of the die-carrying plate or adjusting the floating punches. Finally, the ejection plate 21 could be controlled by pneumatic or hydraulic machines, instead of the mechanical control described hereinbefore.

Nor would it exceed the scope of the invention to use a similar machine for compressing ceramic powders, for instance, instead of metal powders.

What is claimed is:

1. A press for compressing pulverulent products comprising a frame, a floating die-carrying plate resiliently connected to said frame, adjustable stops for said plate, a die mounted in said plate, cores for said die, a mobile top punch cooperating with said die, a bottom punch cooperating with said die and fixed in position during compression, floating bottom punches cooperating with said die, a supporting plate for said bottom punches, a fixed bed plate connected to said frame and supporting said supporting plate, a lifting device for said punch supporting plate, rigid peripheral rods connecting said lifting device and said punch supporting plate leaving the central portion of said punch supporting plate free, a core supporting plate independent of and disposed below said punch supporting plate in said frame and fixed in said bed plate, means for adjusting 'the position of said core supporting plate in the direction of compression, said cores extending freely through said punch supporting plate, rods for adjusting the positions of said floating bottom punches, a plate supporting said adjusting rods independent of and disposed in said frame beneath said core supporting plate, a resiliently acting lifting device for said last-named plate, said adjusting rods extending freely through said core supporting plate and extending freely through said punch supporting plate and a strut freely surrounding each of said adjusting rods and passing freely through said core supporting plate, said struts providing a fixed minimum distance between said supporting plate for said adjusting rods and said supporting plate for said bottom punches.

2. A press as described in claim 1, said resiliently acting lifting device for said support plate for said adjusting rods for said floating punches including a first sheath, said lifting device for said punch supporting plate including a second sheath, said first sheath being slidably mounted in said second sheath and a double acting jack connected tosaid first sheath.

3. A press as described in claim 1 including a tapped freely rotatable bush fixed in said bed plate, said core supporting plate engaging in said bush.

4. A press as described in claim 2 including a rod slidably mounted in said first sheath end engaging said core supporting plate and a double acting jack connected to said rod.

References Cited UNITED STATES PATENTS 1,806,300 5/1931 Lemming 18--16.5 2,338,491 1/1944 Cutler 18-165 2,509,783 5/1950 Richardson 1816.7 2,556,951 6/1951 Weidner 1816.7 2,653,377 9/1953 Seelig 1816.7 X 2,821,748 2/1958 Willi 18-16.7 2,883,703 4/1959 Frank 1816.7 2,932,063 4/1960 Belden et a1. 1816.5 3,132,379 5/1964 Crane 18-165 3,154,812 11/1964 Haller 816.7 3,168,759 2/1965 Johannigman 1816.7 3,172,156 3/1965 Belden 1816.7 3,337,916 8/1967 Smith 18-16.7 3,524,220 8/1970 Davison 1816.7

J. HOWARD FLINT, JR., Primary Examiner 

